Bump version to 2.0.8
Fix RPM build dependencies

RPM build dependencies only listed libaio-devel, while XB needs for
building much more packages which come as dependencies from the PS
sub-builds.
Rename the package to percona-xtrabackup-20[-test]

Rename both the RPM and dpkg packages by appending -20 to their names.
This is so these can share repositories with later versions (for example
2.1.x).
Merge updated build requirements for RPM.
Merged lp:~percona-core/percona-xtrabackup/release-2.0.8.
Bug #1247586: xtrabackup_56 defaults to innodb_checksum_algorithm=crc32

Fixed by changing the default value from 0 to
SRV_CHECKSUM_ALGORITHM_INNODB.

Bug #1248065: innodb_checksum_algorithm should be stored in
backup-my.cnf

Modified both innobackupex and the xtrabackup binary so that
innodb_checksum_algorithm is stored in backup-my.cnf.
Merged lp:~akopytov/percona-xtrabackup/innodb_checksum_algorithm-2.0.